As a technique for observing a micro-structure of an object to be observed, a Raman spectroscopic microscope has been known. Since the Raman spectroscopic microscope can acquire a spatial distribution of molecules or crystal lattices while measuring the frequency of their vibrations, it can be applied to a wide range of technical fields such as material engineering, medical diagnoses, and drug discoveries. In general, the spatial resolution of an observation is restricted by the wave nature of illumination light in such optical observation techniques.
As a technique for improving the spatial resolution, use of structured illumination (e.g., Patent Literature 1) has been known. Further, it has been reported that as a technique for improving the spatial resolution, use of linear illumination (or line illumination) is effective (e.g., Non-patent Literature 2 and 3). These literatures also propose a technique for improving the spatial resolution of a fluorescence microscope by combining results of observations in which the irradiation place of illumination light is shifted (Non-patent Literature 1, 2 and 3).